1. Field of the Invention
The invention relates to an apparatus and method for the insufflation of a gas into a body cavity with emphasis upon controlling and measuring pressure and flow rate.
2. The Related Art
An insufflator is a device utilized for introducing a gas into the abdomen during a surgical procedure to facilitate visualization. Insufflated gases such as carbon dioxide separate tissues and organs in the body. Since the gas has a lower density than the surrounding body tissues and organs, they are delineated on X-rays. Body organs, cavities and intestines are thereby better visualized in radiography.
Historically, insufflators have been utilized for diagnostic and sterilization (low-flow) laparoscopic procedures. More recently, laparoscopic procedures have been applied to more complicated operations lasting for several hours and requiring higher flow capabilities. In these more complex operations, several trocar cannulas and suction devices for removing laser or ESU smoke are usually employed. Gas loss from the abdomen increases as a result of these further inserted devices. Insufflators are therefore required which can deliver high flow rates and maintain pressure without leakage and without impairing safety.
Over the years, there have been improvements reported on insufflation technology. U.S. Pat. No. 3,858,572 (Binard et al.) describes a device including a flexible gas reservoir and a balloon for automatically releasing gas from the reservoir to the atmosphere when a predetermined pressure is exceeded. Over inflation is thereby prevented. The system further includes a syringe for selecting the volume of gas to be introduced into the abdomen.
U.S. Pat. No. 4,464,169 (Sem) describes a single hollow needle utilized for intermittently insufflating gas into the body cavity. Thereafter gas flow is interrupted while the needle is connected with a pressure measuring meter to determine both static and dynamic fluid pressure of the body cavity. Use of the needle insures that the measured pressure is correct because any blood clots and/or tissue will have been blown into the body cavity by the gas during insufflation. The conduit leading to the needle can be split into several branches to allow gas at different pressures and/or volumes to be varied.
U.S. Pat. No. 4,670,006 (Sinnett et al.) reports a fluid infusion device that includes a regulator, driven by a reversible electric motor, for regulating air pressure and flow. The regulator includes a disposable air delivery unit consisting of a filter and a tube removably connected to an air outlet controlled by a normally closed, solenoid-operated infusion valve. Separate pressure transducers detect pressure at various points in the system.
U.S. Pat. No. 4,874,362 (Wiest et al.) describes an insufflation system consisting of pressure reducer, flow meter, pressure meter and lodging control circuit. The device is without noise-generating magnetic valve, and the intra-abdominal pressure can be continuously measured without elaborate switch overs. In this device, the apparatus pressure is varied so that the nominal pressure is more rapidly reached and sudden gas losses can be better accommodated.
U.S. Pat. No. 4,966,578 (Baier et al.) discloses an insufflation system having one measuring transducer detecting dynamic pressure of the gas flow and static intra-abdominal pressure. The system adjusts for electrical changes caused, for example, by entry of a new instrument into the body cavity or a retrocession of flow resulting from differences between inlet and outlet pressures or kinking of a hose.
Most recently, U.S. Pat. No. 5,152,745 (Steiner et al.) reported an insufflator allowing the pressure in the body cavity to be measured without ever reducing the gas flow to zero. An intermediate vessel is bled with its inlet valve closed and outlet valve open. Extrapolation from the pressure decrease then allows identification of the time the pre-set pressure is reached. When an extrapolation calculation indicates a pressure short of that desired, further pumping is continued and the measuring/extrapolation cycle repeated.
The problem with many of the known systems is that they require intricate control valves to control pressure. Since these valves are motor driven, response times are slow. Systems where pressure is controlled with a diaphragm require a linear magnetic device to move the diaphragm; this combination is extremely expensive.
A still further problem with known methods is that they are limited in flow by the low operating pressures required for safety.
Accordingly, it is an object of the present invention to provide an apparatus and method for insufflating a gas into a body cavity which utilize relatively inexpensive valves in a manner that still achieves the rapid adjustment of a gas pressure system.
A further object of the present invention is to provide an apparatus and method for insufflating a gas into a body cavity that can achieve relatively high pressures and flows while nevertheless insuring a high level of safety.
A still further object of the present invention is to provide an apparatus and method for insufflating a gas into a body cavity which is electronically controlled for increased precision, accuracy, and repeatability.
A still further object of the present invention is to provide an apparatus and method for insufflating a gas into a body cavity which achieves adequate gas flow-rates and pressures for all laparoscopic procedures, including procedures with suction of smoke created by laser or electrosurgical treatments.
A still further object of the present invention is to provide an apparatus and method for insufflating a gas into a body cavity which includes self-diagnostics performed to assure unit readiness each time the unit is powered.
A still further object of the present invention is to provide an apparatus and method for insufflating a gas into a body cavity which achieves continuous monitoring of gas circuit pressure and flow-rate and which immediately disables output gas flow when a fault is detected.
A still further object of the present invention is to provide an apparatus and method for insufflating a gas into a body cavity which compensates for over-pressure transients which may be caused by trocar/cannula insertion or instrument manipulation.
These and other objects of the present invention will become more readily apparent through consideration of the following summary, drawings and detailed discussion.